1. Field of the Invention
The present invention relates generally to measurement and calibration of resistance in current sensing applications, and is particularly suited to measurement and calibration of inductor resistance, PCB resistance and relates parasitic resistances.
2. Description of Related Art
Power conversion is an important process which occurs in a variety of systems for many different applications. One such application is in a power converter for a computing system. In a power converter application, a buck converter may be used to provide a stepped-down DC voltage to various components in the system, including the system processor(s). Such systems may benefit by sensing the current at the output of the converter. For instance, DC/DC output current sensing allows for measurement of the power consumed by the load. Current sensing also permits management of load line requirements for processors as well as measurement of power output to determine system efficiency.
In view of this, a variety of current sensing techniques have been developed. For instance, an output current sense resistor may be used in combination with the output inductor of the buck converter. Another technique senses the current through a MOSFET of the buck converter. Yet another technique involves sensing the output current by using the DC resistance of the output inductor itself.
Selecting from among such techniques may involve design choices, such as cost and size of components, as well tolerance levels and sensing accuracy. The DC resistance (“DCR”) of the inductor(s) of power conversion components may have an impact on current sensing. However, DCR and other parasitic resistances may vary based upon a number of factors, including manufacturing tolerances, variation of resistance in a printed circuit board (“PCB”), variations due to solder connections, temperature variations, etc.
Each of these factors may introduce errors into the current sensing process. This may lead to improper voltage provided by the power supply, which in turn may affect the reliability of processors in the computer system. Merely measuring sample circuit boards during manufacture may not provide an adequate baseline DCR for all circuit boards being produced. Resistance measurements may be on the order of milli-ohms to micro-ohms, and there may be lots of variation between different circuit boards.
Systems and methods providing improved current sensing are provided herein.